@ mention: CJK IME — `@美` finds file, `@美术` returns empty

[idfm003]

Bug

Composer @ file search works for one CJK character and dies after the second.

Repro

1. Windows + Chinese IME
2. Type @美 → docs/design/汇总/美术资源清单.md appears
3. Continue typing 术 so the query is @美术 → File group is empty

ASCII paths such as @docs still work.

Expected

@美术 should still match 美术资源清单.md (substring of the filename).

Likely cause

TipTap mention uses allow: !editor.view.composing and only reads nodeBefore text. The second IME-committed character either becomes query 美shu during composition, or splits into a new text node without @.

Env

• Codeg desktop (Windows)
• Chinese IME

[xintaofei]

已修复